1. Field of the Invention
This invention relates to a fuel injection control apparatus of an internal combustion engine from which driving power is transmitted to an output shaft via a gearbox, and particularly to a fuel injection control apparatus of a type wherein a fuel injection quantity is controlled on the basis of a gear position.
2. Description of the Related Art
In fuel injection control apparatuses of the internal combustion engine of related art, the pressure inside an air-intake pipe and a throttle valve opening have been used as parameters for determining a basic injection quantity of fuel; further to this a gear position of a gearbox has been detected, and the fuel injection quantity has been controlled in correspondence with the gear position at the time to obtain a suitable fuel injection quantity corresponding to the operating state of the engine. As methods for determining this gear position, a method in which a known gear position sensor is used and a method in which the gear position is deduced from the outputs of a vehicle speed pulse sensor and an engine speed sensor are known.
However, because gear position sensors are of a battery voltage resistance voltage-dividing type switched by gear changes, the gear position sensor voltage often fluctuates with fluctuation of the battery voltage and load fluctuation at times of sudden acceleration and so on, and this has been a cause of erroneous determination of the gear position. In particular there has been the problem that in high gears, because the voltage range per gear is narrow, erroneous determinations occur easily. With regard to methods using a vehicle speed pulse sensor and an engine speed sensor, on the other hand, although there are methods of the kind set forth for example in Patent Document 1 (JP-A-2004-100590), in which the gear position is discriminated by the ratio of the engine speed to the vehicle speed being compared with a predetermined reference level of gear ratio, with these there has been the problem that because the gear position is deduced by filtering vehicle speed pulse count information from the vehicle speed pulse sensor, a delay arises in the discrimination of the gear position.